Heating systems for bakers&#39; ovens and other heating chambers



J. F. NAYLOR 2,707,925 HEATING SYSTEMS FOR BAKERS OVENS AND OTHERHEATING CHAMBERS May 10, 1955 2 Sheet-Sheei 1 Filed April 28, 1950Inventor $55M fiwms Mon /Q May 10, 1955 J. F. NAYLOR 2,707,925

HEATING SYSTEMS FOR BAKERS OVENS AND OTHER HEATING CHAMBERS Filed April28. 1950 2 Sheets-Sheet 2 HEATING SYSTEMS FOR BAKERS @VENS AND OTHERHEATENG CHAMBERS .loscph Francis Naylor, Newton-le-Willows, England, as-

signor to T. & T. Vicars Limited, l lewton-le willows, England, aBritish company Application April 28, 1959, Serial No. 158,724

Claims priority, application Great Britain April 28, 1949 6 Claims. 3!.l07--63) This invention concerns heating systems for bakers ovens andother heating chambers of the type in which a conveyor adapted to carrythe material to be heat treated'passes between heat exchange ducts whichare part of a closed system circulating a gaseous heat carrying mediumand have heating means at intervals therein.

The principal object of the present invention is to provide a heatingsystem of the above type in which heat radiation from the ducts may hemore efficiently controlled. According to the present invention, in aheating system of tl e type described the heat exchange ducts areconstructed from metal of heavy section and include a plurality ofsubstantially parallel passages longitudinally of the flow of the heatcarrying medium, adjustable balancing dampers being disposed atintervals in each of said passages.

The dampers are preferably arranged in sets, each set comprising adamper in each of said passages in staggered disposition one to theother over a short length of the ducting. A set of dampers may bedisposed lust prior to each heating means in the gaseous flow. Eachdamper may be substantially equal in order to the cross-sectional areaof flow of the passage in which it is disposed and supported by aspindle so as to be rotatable about its transverse axis in respect tothe passage. One end of each spindle may protrude from the oven side andhave adjusting means attached thereto.

The invention will be described further by way of example with referenceto the accompanying drawings in which:

Fig. 1 is a diagrammatic sectional representation of one end of aheating system of the type described.

Fig. 2 is a plan view of a section below the oven roof and above theducting.

Fig. 3 is a sectional elevation on the line Ill-4E of Fig. 2.

Fig. 4 is a sectional end elevation on the line lV-lV of Fig. 3, and

Pig. 5 is a detailed View of one form of adjusting means.

Referring to the diagrammatic Fig. 1 a heating systern of the typedescribed is provided in a long oven 11 in which the biscuits are to bebaked. An endless conveyor 12 passes over a roll 13 outside one end ofthe oven H and between two lengths l4, 15 of heat exchange ducts. Itthen passes over a similar roll (not shown) outside the other end of theoven and back to the first roll 13 along the bottom of the oven. Theupper and lower lengths 14, 15 of heat exchange ducts are connected bytrunks at one end of the oven (not shown) and at the other end of theoven the lower length of ducting 15 exhausts to a circulating fan 16which feeds the upper length of ducting 14. An escape chinmney 1?controlled by a damper 18 is provided just after the fan outlet. Thedirection of circulation of a heat carrying gaseous medium is indicatedby the arrows. At intervals along the ducts 14, 15 enlarged portions 19are provided at which heating means are disposed and dampers areprovided at intent; aerlid 2,707,925 Patented May it), 1955 tervalswithin the ducts. The ducts are manufactured from metal of heavysection.

The more detailed Figs. 2, 3, 4, and 5 show by way of example a portionof the upper duct 14. A length of ducting is cast and is supported inposition in the oven by means (not shown), but which usually consist ofsuitable girders and heat insulating substances, with a small gap 22between the next succeeding section. Connection of the succeedingportions which is also not shown usually consists of an encircling lapof asbestos topped by steel plates and bolted to one section only or"-the duct to allow for expansion. The duct 14 has three parallel passages14a, 14b, 14c separated by dividing walls 23, 24 and at intervals setsof dampers are provided, each set being preferably just prior to aheating r cans in the gaseous flow through these passages. The diviwalls 23, 24 are interrupted at each enlarged portion 1? so that theheating means 20 may extend freely transversely of the ducting. Theinterruption of the longitudinally extending dividing walls at eachenlarged portion lit provides openings or passages permitting gaseousmedium to flow from one longitudinally extending parallel passage intoanother longitudinally extending parallel passage assuming, of course,that the pressure differential is such as to cause the gaseous medium toflow in the manner described. Since the heatmeans 2d extends freelytransversely of the ducting, said eating means passing through saidopenings or pass es provided by the interruption of the longitudinald1 gdividing walls 23, 24, it is apparent that s or passages aresubstantially in alignment a transverse to the length of the ducting. Acomplete set of dampers comprises one damper 25,

-lled at one end in an outer or dividing wall according to which damperit supports and at the other end the oven. The spindles 28, 29, 34)support their respective dampers 25, 2e, 27 along their centraltransverse axes when the dampers 25, 26, 27 are disposed nearlyvertically in the passages, ll la, 14b, 1 the passages are not quitecompletely blocked (see Fig. 4). The ends or" the spindles 25%, 29, 3dwhich protrude from the oven ii are provided with handles 28a, 2%, 343a,the main portions of which are at right angles to the spindles. A springloaded stud 23b, 29b, 3% at the outer end of each handle 28a, 29a, 39ais able to move in a circular are over the face of a quadrant secured tothe oven wall in which recesses are provided. The spring loaded studs23b, 29b, 3% can therefore engage in any of the recesses as desired andthe recesses are conveniently marked to indicate the position of therespective dampers.

Fig. 5 shows an adjusting handle similar to those in Figs. 2, 3 and 4but with the handle upwardly extending instead of downwardly extendinEither type of handle could be adapted for satisfactory use but it isimportant that the dampers should never reach a completely closedposition. In other words the gaseous flow must never be whollyinterrupted. To prevent this a suitable stop 34 may be provided on thequadrant of the adjusting means to prevent further movement of thehandle. in the embodiment shown in Figs. 2, 3 and 4 a suitable stopwould be to the right of each handle 28a, 29a, 39a.

The bottom of each section of ducting of the upper length 14 is providedwith downwardly projecting. cor-.

U of the bottom length will, of course, have similar corrugations ontheir upper surfaces. These corrugated lengths have also a greaterthickness than the rest of the ducting.

In operation the ducts being constructed of metal of heavy section, arecapable of accumulating a large amount of heat and provide an efficientmeans of heat radiation to the articles which pass between them on theconveyor. The space between the upper and lower lengths of ductingcomprises the treatment Zone.

The heating means 2t.- acting at intervals in the ducts 14, 15 may be,for instance, burners of the oil or gas type and serve to re-heatperiodically the gaseous medium as it flows along the ducting.

Without the dampers 25, 26, 27 described above it would be impossible tocontrol the heat radiation from the ducting except by controlling theamount of fuel or air supplied to the burners. This method of controlwould be difificult to carry out in an efficient manner. By means of thedampers, 25, 26, 27 however, the oven 11 is potentially divisible intosubstantially independent heating zones both longitudinally andtransversely and accurate control of heat distribution within the oven11 can be achieved both longitudinally and transversely. This control isfacilitated by the convenient external adjusting means provided on eachdamper spindle 28, 2%, 30.

In Figs. 2, 3 and 4, for instance, the dampers 25, 26 in two adjoiningpassages 14a, 1412 are fully closed whilst the third damper 27 is fullyopen. This state of affairs would tend to increase the amount of heatsupplied to the radiating surface of the ducting which surrounds the twoadjoining passages 14a, 14b and is just prior to the dampers whilst theradiating surfaces of these passages 14a, 1411 after the dampers in thedirection of the gaseous flow would be somewhat cooler. The passage 14ccontaining the open damper 27 would tend to remain at substantiallyequal temperatures at all parts. It might be necessary, however, toadopt the damper disposition just referred to in order to maintain equaltemperatures transversely of the oven. In other words, the respectivedampers can be positioned to permit a desired rate of flowlongitudinally of the ducting and a desired amount of flow from onelongitudinal passage into another longitudinal passage through anopening in a dividing wall located at an enlarged portion 19, or througha plurality of said openings. It is apparent that the ability to controlthe amount of straight longitudinal flow and to control also the amountof flow from one parallel passage to another parallel passage provideswhat can be described as a two-dimensional control of heat distributionthroughout the length of the oven. Without such two-dimensional control,the oven heat tends to vary not only lengthwise of the oven but alsotransversely thereof. This may be due to the type of burner used or toinequalities of the heating effect in normal circumstances which canarise in unexpected ways. This example, however, serves to indicate themany different effects of damper manipulations which can be obtained andin practice it is possible, along with burner control, to accuratelyadjust the heat radiating strength of any part of the ducting asrequired.

I claim:

1. A heating system for bakers ovens and like heating chamberscomprising a plurality of heavy metal duct sections serially connectedtogether in a closed system, means to circulate a gaseous heat carryingmedium longitudinally through said duct sections, a longitudinallyextending partition wall positioned within said duct sections andproviding parallel longitudinally extending passages within said ductsections, said partition wall being interrupted for a portion of itslength to define an opening permitting gaseous medium to flowtransversely from either parallel passage to the other parallel passage,and an independently adjustable damper positioned in each d of saidparallel passages immediately in advance of said partition wall openingin the direction of flow of said gaseous medium, said dampers providingcontrol of flow of gaseous heat carrying medium longitudinally alongsaid parallel passages and said partition wall opening permittinggaseous heat carrying medium to flow from either parallel passage to theother parallel passage to effect heat redistribution in a directiontransverse to the length of said duct sections.

2. A heating system for bakers oven and like heating chambers comprisinga plurality of heavy metal duct sections serially connected together ina closed system, means to circulate a gaseous heat carrying mediumlongitudinally through said duct sections, a longitudinally extendingpartition wall positioned within said duct sections and providingparallel longitudinally extending passages within said duct sections,said partition wall being interrupted for a portion of its length todefine an opening permitting gaseous medium to flow transversely fromeither parallel passage to the other parallel passage, gaseous mediumheating means located at and extending freely through said partitionwall opening in a direction transverse to the length of said ductsections, and an independently adjustable damper positioned in each ofsaid parallel passages immediaely in advance of said partition wallopening in the direction of flow of said gaseous medium, said dampersproviding control of flow of gaseous heat carrying medium longitudinallyalong said parallel passages and said partition wall opening permittinggaseous heat carrying medium to flow from either parallel passage to theother parallel passage to effect heat redistribution in a directiontransverse to the length of said duct sections.

3. A heating system for bakers ovens and like heat ing chambersaccording to claim 2 wherein said partition wall is interrupted atintervals throughout its length to define a plurality of openingspermitting gaseous medium to flow transversely from either parallelpassage to the other parallel passage, there being a heating meanslocated at and extending freely through each partition wall opening in adirection transverse to the length of said duct sections.

4. A heating system for bakers ovens and like heating chamberscomprising a plurality of heavy metal duct sections serially connectedtogether in a closed system, means to circulate a gaseous heat carryingmedium longitudinally through said duct sections, longitudinallyextending partition walls positioned within said duct sections andproviding a plurality of parallel longitudinally extending passageswithin said duct sections, said partition walls being interrupted atintervals throughout the length of said walls to define openingspermitting gaseous medium to how transversely from one parallel passageto another parallel passage, and an independently adjustable damperpositioned in each parallel passage and immediately in advance of eachof said partition wall openings, said dampers providing control of flowof gaseous heat carrying medium longitudinally along said parallelpassages and said partition wall openings permitting gaseous heatcarrying medium to flow from one parallel passage into another parallelpassage to effect heat redistribution in a direction transverse to thelength of said duct sections.

5. A heating system for bakers ovens and like heating chambers accordingto claim 4 including heating means located at and extending freelythrough each partition wall opening in a direction transverse to thelength of said duct sections.

6. A heating system for bakers ovens and like heating chamberscomprising a plurality of heavy metal duct sections serially connectedtogether in a closed system, a portion of said serially connected ductsections being enlarged, means to circulate a gaseous heat carrying medium longitudinally through said duct sections, longitudinally extendingpartition \valls positioned within said duct sections and providing aplurality of parallel longitudinally extending passages within said ductsections, each of said partition walls being interrupted at saidenlarged portion of said serially connected duct sections to defineopenings permitting gaseous medium to flow transversely from oneparallel passage to another parallel passage, heating means located atand extending freely through each partition wall opening in a directiontransverse to the length of said duct sections, and an independentlyadjustable damper positioned in each parallel passage and immediately inadvance of each of said partition wall openings, said dampers providingcontrol of flow of gaseous heat carrying medium longitudinally alongsaid parallel passages and said partition wall openings permittinggaseous heat carrying medium to flow from one parallel passage intoanother parallel passage to efiect heat redistribution in a directiontransverse to the length of said duct sections.

References Cited in the file of this patent UNITED STATES PATENTS1,657,959 Crosland Jan. 31, 1928 1,772,920 Smoot Aug. 12, 1930 2,501,765Dumbleton et a1 Mar. 28, 1950 FOREIGN PATENTS 504,950 Great Britain May3, 1939

